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The featured article for Wednesday, 14 February 2018 is Paxillus involutus.

Paxillus involutus, commonly known as the brown roll-rim, common roll-rim, or poison pax, is a basidiomycete fungus widely distributed across the Northern Hemisphere. It has been unintentionally introduced to Australia, New Zealand, and South America, where it has likely been transported in soil with European trees. Various shades of brown in colour, the fruit body grows up to 6 cm (2.4 in) high and has a funnel-shaped cap up to 12 cm (5 in) wide with a distinctive inrolled rim and decurrent gills that may be pore-like close to the stipe. Although it has gills, it is more closely related to the pored boletes than to typical gilled mushrooms. It was first described by Pierre Bulliard in 1785, and was given its current binomial name by Elias Magnus Fries in 1838. Genetic testing suggests that Paxillus involutus may be a species complex rather than a single species.

A common mushroom of deciduous and coniferous woods and grassy areas in late summer and autumn, Paxillus involutus forms ectomycorrhizal relationships with a broad range of tree species. These benefit from the symbiosis as the fungus reduces their intake of heavy metals and increases resistance to pathogens such as Fusarium oxysporum. Previously considered edible and eaten widely in Eastern and Central Europe, it has since been found to be dangerously poisonous, responsible for the death of German mycologist Julius Schäffer in 1944. It had been recognised as causing gastric upsets when eaten raw, but was more recently found to cause potentially fatal autoimmune hemolysis, even in those who had consumed the mushroom for years without any other ill effects. An antigen in the mushroom triggers the immune system to attack red blood cells. Serious and potentially fatal complications include acute renal failure, shock, acute respiratory failure, and disseminated intravascular coagulation.

This recording reflects the Wikipedia text as of 00:15 UTC on Wednesday, 14 February 2018.